The invention generally relates to guide catheters, specifically relating to guide catheters having a rotating working element at the distal end. The invention more particularly concerns a guide catheter capable of being used in conjunction with a guidewire, where the catheter provides a rotating working element at the distal end, such as may be used for traversing totally occluded vessels.
In the field of interventional cardiology there is a need for a percutaneously introduced intravascular device that can open totally occluded vessels. Many patients are found at diagnosis to have one or more totally occluded coronary vessels, and in the lower limbs there are even more aggressively closed vessels. Currently the options for solving these problems are as follows: A) attempt to traverse the blockage using guidewires and then follow up by dilatation and the placement of a stent: B) use a blunt dissection device like that manufactured by Cordis under the trade name ‘LUMEND’ device to ease the occlusion open enough to pass a wire, along which a subsequent dilatation balloon and stent are passed: C) use an electrocautery delivery wire, like that sold under the trade name ‘SAFECROSS” by Intra Luminal Therapeutics, to burn a hole through the blockage and then pass a subsequent balloon dilatation catheter with stent to open the vessel: D) if all else fails pass the patient on to surgery.
All methods A) through C) have their limitations. Method A) can be extraordinarily slow, as long as two hours. Method B) is also slow and has exhibited a high degree of perforation. Method C) works well and can deal with seriously calcified lesions but could benefit by having some additional features to reduce the procedure time. Consequently there is the need for a device that can open these occlusions relatively rapidly with little risk of perforation.
The subject of this application is a device that delivers rotary energy to an atraumatic rotating tip, such as a tissue penetrating element, which, in one embodiment, can best be described as half of an elliptical spheroid with a number of flats along its sides. These flats work rather like rotating a blunt screwdriver into a piece of soft wood with the flats gradually working the fibers of the wood apart. Based on our previously patented devices such as the Kensey catheter (e.g., U.S. Pat. No. 4,747,821), we believe that such a tip can open the vessel with a low degree of trauma.
One disadvantage to current rotary devices is the need to pass the entire rotary drive over a guidewire, known as over-the-wire systems (OTW) to permit navigation of the tortuous anatomy on the way to the blockage. Such an arrangement requires a very long guidewire (300 cm) to permit control of the wire from the proximal end when the rotary device is placed along or removed from the wire.
There is also the problem of navigation as one gets close to the blockage, because by definition the wire cannot be pushed past the blockage. These problems have made the use of rotary devices in such total occlusion applications limited to virtually straight vessel anatomy such as is found in the femoral artery. Consequently in order to make a more acceptable device one preferably would incorporate steering at the distal tip to overcome the navigation problem, and a optionally monorail wire guidance (also known as a rapid exchange system) which allows the guidewire to exit the catheter at some distance typically 10-20 cm proximal from the distal tip, to allow the use of short, more manageable guidewires.
In addition there is the need for such a device to be very small in diameter (1 mm or less) if the penetration of the occlusion is to liberate a minimum of debris and if the device is to be directed into distal coronary vessels of <2 mm diameter.
All currently known rotary devices used by the cardiologist are total length OTW devices, requiring the use of 300 cm wires in order to be placed over a guidewire or removed from the guidewire. These rotary devices are placed over the guidewire, with the guidewire passageway being centrally located or coaxial to the device, in order to ensure the rotating portion remains centered about the guidewire. In order to be employed in a rapid exchange fashion, and be capable of being placed over shorter (e.g. 150 cm) guidewire, the guidewire must exit from the revolving shaft at some point, typically about 10 cm-20 cm proximal of the distal tip. Such a requirement makes it necessary to provide for some manner of offset drive at this transition point, with the input drive shaft passing alongside the guidewire exit portion off center from the guidewire center.
It should be understood that the same problem of requiring a double length guidewire could also occur with other OTW devices such as rotary intravascular ultrasound scanners, and rotary optical scanners for optical coherence tomography. Hence the systems described in this application should be considered to be applicable to any device used within a living being that incorporates a rotary input and would benefit from a means to reduce the guidewire length.
Also, no small (3 mm diameter or less) current rotary intraluminal devices incorporate a steerable distal tip. Innovative steering concepts are required to permit the steering function to exist alongside the rotary drive shafting.
In addition there are situations when special purpose guidewires such as those marketed under the name SAFECROSS guidewires (mentioned elsewhere in this application) or other guidewires could benefit from passage through a firm steerable catheter tip which could provide backup or support in order to steer the guidewire into an adjacent furcation, where otherwise the soft wire would tend to buckle without the additional support provided by the steerable catheter tip.
There is also the need for a low friction steerable catheter tip to permit the passage of straight stiff guidewires into a selected branch of a furcation. The straight stiff wire is often needed to navigate and penetrate a firm blockage distal of the furcation, but the anatomy demands a guidewire with a prebent tip to allow entry into the preferred branch. Clearly these are conflicting requirements, and a steerable catheter capable of guiding the stiff wire to the desired location may be beneficially employed. It is recognized that the steerable catheter may also employ a rotating component through which the stiff wire is advanced within the steerable catheter, where the rotation will serve to minimize friction forces encountered when advancing the stiff wire through the guide catheter.
It is the intent of this invention to overcome these and other shortcomings of the prior art.